US air force Staff Sgt Luis A Walker arrives at his court-martial at Lackland Air Force Base. Photograph: Jerry Lara/AP

An air force instructor convicted of raping a female recruit and sexually assaulting several others is due back in court on one of the nation's busiest training bases on Saturday for the start of the sentencing phase of his court-martial.

Staff Sgt Luis Walker, who faced the most serious charges in a sweeping sex scandal involving Lackland Air Force Base instructors, could be sentenced to up to life in prison and dishonorably discharged. A military jury convicted him on Friday on all 28 counts he faced, including rape, aggravated sexual contact and multiple counts of aggravated sexual assault.

Prosecutors say from October 2010 through January 2011, Walker sexually assaulted or had improper sexual or personal contact with at least 10 female recruits. Lackland is where all air force recruits go through basic training.

Walker is among 12 Lackland instructors investigated for sexual misconduct toward at least 31 female trainees, and among the six charged on counts ranging from rape to adultery.

Several of Walker's alleged victims testified during his court-martial, including one who described how Walker lured her into an office and sexually assaulted her on a bed, ignoring her pleas to stop.

The women told jurors that Walker gained their trust to get them alone in his office or an empty dormitory, where he then forced them into kissing, touching or intercourse. The alleged sexual misconduct among instructors at the base apparently began in 2009, but the first woman didn't come forward until last year. The women who testified against Walker said they didn't tell anybody at first because they feared being booted from the air force.

According to prosecutors, Walker had sexual intercourse with four of the 10 female recruits. He was also accused of making flirtatious or sexually suggestive comments, sending inappropriate text messages and sometimes groping his recruits.

Prosecutors also accused Walker of forcing five recruits to engage in sexual acts with him by threatening their military careers, and they said he intimidated two of the women into lying about his alleged misconduct.

Meanwhile, the air force said Friday that the case against another former training instructor was referred to a general court-martial.

Staff Sgt Craig LeBlanc is charged with sexual misconduct, obstructing justice and making a false official statement. He is accused of using his post as a military instructor to sexually assault and pursue a sexual relationship with one female trainee, and have a wrongful sexual relationship with another. No trial date was set.

One of the other instructors charged in the case, Staff Sgt Peter Vega-Maldonado, pleaded guilty in June, admitting he had sex with a female trainee in exchange for a sentence of 90 days' confinement. He later acknowledged he had been involved with a total of 10 trainees – a number previously unknown to investigators.

Lackland has about 475 instructors for the approximately 35,000 airmen who graduate every year. About one in five is female, pushed through eight weeks of basic training by a group of instructors, 90% of whom are men.